1. Field of the Invention
The present invention relates to a photocurable and thermosetting resin composition useful for, in particular, solder resists for direct laser imaging, and also relates to a cured product of the photocurable and thermosetting resin composition, and a printed circuit board patterned using the same.
2. Description of the Related Art
In order to insure the accuracy of positioning in the formation of a solder resist on a printed circuit board, laser direct imaging technique for directly drawing an image by laser according to CAD data has been drawing attention. However, commercially available solder resists require very high exposure energy from 200 to 500 mJ, and thus require much time for direct imaging exposure.
In order to solve the problem, photopolymerization initiators having a high photopolymerization capability, and compositions containing the photopolymerization initiators have been proposed (for example, see Patent Document 1: Jpn. Pat. Appln. KOKAI Publication No. 2001-235858 and Patent Document 2: International Publication No. WO02/096969). By these techniques, a sufficient photopolymerization capability is provided even with bright lines from 350 to 370 nm. However, the rate of photopolymerization is so high that the deep and surface curability are not sufficient. In addition, deactivation of the photopolymerization initiator on the circuit by heat treatment causes striking deterioration of the sensitivity, which results in ablation on the copper circuit.